Chapter 3 Bacterial Cell Structure

Bacterial shape

Filamentous

Complex

Filamentous

make hyphae -> mycelium

similar to fungi

Ex: cyanobacteria & Streptomyces

Complex

(can change)

create fruiting bodies -> spores at top

Ex: Myxococcus

Bacterial Arrangement

Arrangement determined by

plane of division

separation or not

Strepto

chain

stay together

sarcina

cube

4 in front, 4 in back

cocci

ball

bacilli

rods

Bacterial size

smallest - 0.3 um (Mycoplasma)

avg rod - 1.1 - 1.5 x 2 - 6 um (E. coli)

very large - 600 x 80 um Epulopiscium fishelsoni

Size - shape relationship

Nutrient uptake

Protective mechanism from predation

Rate at which nutrients and waste products move in and out

is generally inversely proportional to cell size

transport rate depends

on membrane surface area (SA) available in comparison to cell volume (V)

Size limit?

there is a limit on sizing

Which are more efficient transporters rods or cocci?

rods are more efficient

!!! What does bacteria release

eat and release waste quickly

Haemophilus Influenzae

does not cause flu (is secondary infectious agent)

can cause meningitis

too large bacteria

cant be eaten

too small bacteria

cant eat

Surface area to volume ratio

the larger the SA/V ration, the more easily the nutrients can move

collision surface area

Small cells are

more effective transporters

cell size is

limited for effective transport

As cell size increases

the SA/V ratio decreases and thus transport is less effective

SA/V equation

3/r

ex: radius is 2 um

3/2 = 1.5

Bacterial cell organization

What is the order of cell envelope?

Inside to outside

Cell membrane, peptidoglycan, slayer (Outer membrane (LPS), capsule/slime layer

only living domains have

cell membrane

What can bacteria have

Peptidoglycan

What is the capsule/slime layer

extra layer of protection

the cell envelope is

the cell membrane and anything about it

Gram negative

area between the cell membrane and outer membrane, including peptidoglycan

Gram positive

area between cell membrane and start of peptidoglycan

What are plasmids

extra chromosomal double stranded DNA

Inside the cell is the

cytoplasm

Bacterial Cytoplasmic structure

Cytoskeleton

Intracytoplasmic membranes

Inclusions

Ribosomes - translation

Nucleoid and plasmids

Examples of bacterial cytoskeleton molecules

FtsZ

MreB

CreS

FtsZ

many bacteria; tubulin homologue

replication; find middle of cell

MreB

many rods; acting homologue

E. coli

CreS

maintains curve shape; intermediate filament homologue

Storage inclusions

nutrients, metabolic end products, energy, building blocks

where do bacteria grow

in a hypotonic environment

in nutrient poor habitats

Glycogen

glucose storage

storage of Carbon

storage

poly-B-hydroxybutyrate (PHB)

storage of Phosphate

polyphosphate granules

storage of Sulfur

sulfur globules

storage of Amino acids

cyanophycin granules

Inclusions - Movement

Gas vacuoles

full - go up

empty - fall

Magnetosomes

cytoskeletal protein MamK

model bacteria

Magnetospirillum gryphiswaldense

Magnitite particles

when dispersed, stay where they are

linearize -> go towards the bottom

Plasmids and episomes

Extrachromosomal DNA

plasmid

episomes

plasmid

exist and replicate independently of chromosome

episomes

integrate into the chromosome

Classification via mode of

existence, spread, function

a) Conjugate plasmids

conjugation

b) R plasmids

resistance to antibiotic

c) Virulence plasmids

making bacteria more harmful

d) Col plasmids

kill or inhibit growth of other bacteria

What is this used in

research/biotechnology

Plasma Membrane Functions

encompasses the cytoplasm; absolute requirement for all living organisms

what type of membrane is it

selectively permeable membrane

Interacts with external environment

receptors for detection of and response to chemicals in surroundings

transport systems

metabolic processes

ETC for metabolism

electron transport chain

fluid mosacic model

Amphipathic lipids

two parts

hydrophobic and hydrophilic parts

Membrane proteins

peripheral or integral

clustered

Protein content and lipid bilayer varies in

thickness

Peripheral membrane protein

not embedded in membrane

integral membrane protein

embedded in membrane

transmembrane proteins

go across membrane

all transmembrane proteins are

integral

not all integral proteins are

transmembrane

Bacterial lipids

saturation levels reflect

environmental conditions

Bacterial membranes lack

sterols

bacterial membranes contain

hopanoids

hydrophobic

eukaryotes have

sterols in their membrane

sterols are

usually absent in prokaryotes, except in Mycoplasma (has cell membrane, no cell wall)

Methods for uptake of nutrients

some nutrients enter by

passive diffusion

Transport mechanisms

facilitated diffusion

active transport

group translocation

Simple transport

driven by the energy in the proton motive force

group translocation

chemical modification of the transported substance driven by phosphoenolpyruvate

ABC transporter

periplasmic binding proteins are involved and energy comes from ATP

active transport

low -> high ; uses energy

Passive vs facilitated diffusion

Passive diffusion

H2O, O2, and CO2

Facilitated diffusion uses

permeases

a ----- concentration gradient is required

smaller

includes

glycerol, sugars, and amino acids

more prominent in

eukaryotic cells

plateau in facilitated diffusion represents

the saturation effect that is seen whenever a carrier protein is involved in transport

Active transport

molecules against the gradient

needs energy

active transport involves

permeases

three classes of active transport are

primary active transport

secondary active transport

group translocation

ATP-Biding cassette (ABC) transporters

is a type of primary active transporters

atp (energy source)

uniporter

primary active transporters

move 1 thing at a time

ABC transporters are

found in all 3 domains of life